The present invention relates, in general, to vehicle seat adjusters.
Description of the Art
Power seat adjusters are a popular option on many automotive vehicles and are frequently offered as standard equipment on higher priced vehicles. Such power seat adjusters are primarily used on the driver's seat and, sometimes, on the front passenger seat of the vehicle to provide selective horizontal fore and aft and vertical movement of the seat as well as seat back recliner movement to accommodate occupants of different size and height as well as to provide a comfortable seating position to suit each occupant's preference.
Such power seat adjusters typically carry a seat support frame which supports the seat bottom and sometimes the seat back of a vehicle seat. The seat support frame is mounted on first and second, spaced track assemblies, each formed of an upper track which is connected to the seat support frame and which is slidably mounted on a lower track anchored to the vehicle floor. A horizontal drive mechanism typically includes a bi-directional electric motor which rotates a drive shaft extending outward from the motor to a gear assembly or box. In one arrangement, the gear box rotates a lead screw extending longitudinally along a track assembly. A drive block is fixedly mounted to one of the tracks and threadingly receives the lead screw to cause reciprocal, horizontal movement of the upper track and the attached seat support frame upon selective energization of the drive motor and the drive shaft. Typically two drive shafts, gear boxes, lead screws and drive nuts are employed in a horizontal drive, one set for each track assembly.
As the various drive motors are mounted between the track assemblies, the drive motor output shafts and the drive shafts connected thereto are typically oriented perpendicular to the axis of the associated lead screw. In order to transmit rotation and drive force between the output shaft of the drive motor and the drive shaft connected thereto to the 90.degree. offset lead screw, each gear assembly or box typically includes a worm gear which is insert molded on one end of the associated lead screw. A worm is rotatably mounted in the gear box housing in meshing engagement with the worm gear and is connected to one of the drive motor output shafts or to one of the drive shafts so as to rotate the worm gear and thereby the lead screw upon bi-directional energization of the selective drive motor. Thus, each drive motor requires a separate gear assembly for each lead screw driven by the drive motor. This results in additional components on the power seat adjuster which add cost and take up valuable space in the already crowded space below a vehicle seat.
For a typical horizontal drive mechanism in a power seat adjuster, the horizontal drive mechanism includes one drive motor which may be mounted centrally or intermediately between the pair of track assemblies, two flex shafts extend from the drive motor to two gear boxes each connected to a lead screw, with one gear box and one lead screw associated with each of the pair of track assemblies.
It is also known to mount the drive nuts or drive blocks for self-alignment in a holder or housing to compensate for any misalignment between the lead screw or drive shaft. Thus, it is known to mount a drive nut in a lower track for rotation about a vertical axis as well as vertical sliding movement. Drive nuts have also been movably mounted in a housing affixed to one of the upper or lower tracks of a vehicle track assembly for movement in one of two mutually exclusive axes or planes relative to the housing.
The track assemblies for power seat adjusters have been constructed in a manner to resist separation of the upper track from the lower track during high force loading, such as occurs during a collision in which seat momentum, seat belt inertia, and occupant loading exert considerable force on the upper track which tends to separate the upper track from the lower track. To resist these forces, it is common to structurally design the upper and lower tracks with a sufficient strength and material cross-section to prevent track separation.
It is also known to provide interlocking notches and fingers in the upper and lower tracks which are normally spaced apart during regular sliding movement of the track assembly; but which are urged into fixed engagement to lock the upper track to the lower track during high impact loads. However, this has resulted in a larger cross-section track assembly which reduces the already minimal amount of open space below the vehicle seat and between the pair of track assemblies.
In vehicle power seat adjusters having independently elevatable front and rear seat drive mechanisms, such front and rear seat elevation is typically implemented by front and rear torsion tubes which are rotatably mounted between the front and rear ends of the pair of track assemblies. Motion linkages are fixedly mounted on the front and rear torsion tubes and are interconnected to the front vertical and rear ends of the seat support to elevate or lower the front and rear edges of the seat upon rotation of the torsion tubes by independent drive motors.
The torsion tubes have been typically mounted in the track assemblies by means of conventional bushings and separate brackets. In addition, a separate spacer has been mounted about each end of each torsion tube adjacent to the inboard surfaces of the track assemblies to provide a set spacing between the track assemblies and the motion linkages to maintain the motion linkages and the torsion tubes in the set design position.
However, it has been found that further improvements can be made to a vehicle power seat adjuster and it would be desirable to provide an improved power seat adjuster for a vehicle seat which overcomes certain deficiencies found in previously devised power seat adjusters. It would be desirable to provide a power seat adjuster which has only a single, horizontal drive motor and a single horizontal drive shaft; but which is still capable of simultaneously moving both movable tracks of the pair of track assemblies. It would also be desirable to provide a power seat adjuster having a unique horizontal drive system and drive nut mount which has a minimal number of components for a reduced cost, improved sound quality, reduced operating noise, more efficient assembly and reduced vibration.
It would also be desirable to provide a power seat adjuster which has a unique track assembly design which provides self-locking features during high impact loads. It would also be desirable to provide a power seat adjuster having a track assembly which exhibits a minimal lateral dimension or width for increased open area beneath the seat.
It would also be desirable to provide a unique track mounting arrangement which enables the track assemblies to be attached to the raised central tunnel portion of the vehicle floor in a manner to place the mounting fasteners in shear. It would also be desirable to provide a power seat adjuster having a track assembly mounting arrangement which enables the lateral dimension or width or the track assembly to be made as small as possible.
Finally, it would be desirable to provide a vehicle power seat adjuster having a unique torsion tube mounting arrangement having a minimal number of components.